U.S. patent number 10,503,127 [Application Number 15/919,575] was granted by the patent office on 2019-12-10 for method for safe control of gas delivery to an electron microscope sample holder.
This patent grant is currently assigned to PROTOCHIPS, INC.. The grantee listed for this patent is PROTOCHIPS, INC.. Invention is credited to William Bradford Carpenter, John Damiano, Jr., Daniel S. Gardiner, David P. Nackashi, James Rivenbark, Rebecca Thomas, Mark Uebel, Franklin Stampley Walden, II, Michael Zapata, III.
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United States Patent |
10,503,127 |
Gardiner , et al. |
December 10, 2019 |
Method for safe control of gas delivery to an electron microscope
sample holder
Abstract
System and method for safely controlling the containment of gas
within a manifold system and the delivery of gas to a sample holder
for an electron microscope for imaging and analysis.
Inventors: |
Gardiner; Daniel S. (Wake
Forest, NC), Damiano, Jr.; John (Apex, NC), Nackashi;
David P. (Raleigh, NC), Carpenter; William Bradford
(Asheville, NC), Rivenbark; James (Raleigh, NC), Uebel;
Mark (Morrisville, NC), Zapata, III; Michael (Cary,
NC), Thomas; Rebecca (Valparaiso, IN), Walden, II;
Franklin Stampley (Raleigh, NC) |
Applicant: |
Name |
City |
State |
Country |
Type |
PROTOCHIPS, INC. |
Morrisville |
NC |
US |
|
|
Assignee: |
PROTOCHIPS, INC. (Morrisville,
NC)
|
Family
ID: |
55179729 |
Appl.
No.: |
15/919,575 |
Filed: |
March 13, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180203423 A1 |
Jul 19, 2018 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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14816332 |
Aug 3, 2015 |
9915926 |
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62032612 |
Aug 3, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J
37/20 (20130101); G05D 7/0635 (20130101); G01M
3/3272 (20130101); G05B 9/02 (20130101); H01J
2237/2007 (20130101); H01J 2237/2802 (20130101); H01J
2237/006 (20130101); H01J 2237/2002 (20130101); H01J
2237/182 (20130101); H01J 37/18 (20130101) |
Current International
Class: |
G05D
7/00 (20060101); G05B 9/02 (20060101); H01J
37/20 (20060101); G05D 7/06 (20060101); G01M
3/32 (20060101); H01J 37/18 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Netherlands Enterprise Agency,Search Report and Written Opinion,
Netherlands Patent Application No. NL2015258 dated Jul. 13, 2016,
pp. 1-14. cited by applicant .
Creemer, J. Fredrik, et al., A MEMS Reactor for Atomic-Scale
Microscopy of Nanomaterials Under Industrially Relevant Conditions,
Journal of Microeletromechanical Systems, Apr. 2010, pp. 254-264,
vol. 19, No. 2. cited by applicant .
Xin, Huolin L., et al., In Situ TEM Study of Catalytic Nanoparticle
Reactions in Atmospheric Pressure Gas Environment, Microscopy and
Microanalysis, Dec. 2013, pp. 1558-1568, XP-001585594, Microscopy
Society of America 2013. cited by applicant .
WIPO, International Preliminary Report on Patentability for PCT
Patent Application No. PCT/US2015/043381, dated Feb. 7, 2017. cited
by applicant .
PCT, International Search Report and Written Opinion in
International Application No. PCT/US2015/043381 dated Nov. 30,
2015. cited by applicant .
USPTO, Office Action in U.S. Appl. No. 14/816,332 dated Aug. 8,
2017. cited by applicant .
USPTO, Notice of Allowance in U.S. Appl. No. 14/816,332 dated Dec.
6, 2017. cited by applicant .
R. Ubic, Standard Operating Procedure, Hitachi S-3400N-II Scanning
Electron Microscope (SEM), Nov. 7, 2011, pp. 1-8. cited by
applicant.
|
Primary Examiner: Connolly; Mark A
Attorney, Agent or Firm: NK Patent Law
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser.
No. 14/816,332 filed on Aug. 3, 2015 and entitled "Method for Safe
Control of Gas Delivery to an Electron Microscope Sample Holder,"
and claims priority to U.S. Provisional Patent Application No.
62/032,612 filed on Aug. 3, 2014 and entitled "Method for Safe
Control of Gas Delivery to an Electronic Microscope Sample Holder,
" which is hereby incorporated herein in its entirety.
Claims
What is claimed is:
1. A system comprising: an electron microscope sample holder having
a cell; and a gas delivery system comprising: a gas source device
configured for fluid communication with the cell; a gas destination
device configured for fluid communication with the cell; a pressure
sensor configured for fluid communication with at least one of the
cell, the gas source device, and the gas destination device; at
least one valve; an intermediary valve between the at least one
valve and an inlet port; and a controller configured for monitoring
the pressure sensor and signaling control of the valve.
2. The system of claim 1, further comprising a mass flow
controller.
3. The system of claim 1, wherein the gas source device comprises a
tank.
4. The system of claim 1, wherein the gas destination device
comprises at least one of a tank and a pump.
5. The system of claim 1, wherein: the at least one valve closes
when not electrically activated.
6. The system of claim 1, wherein the pressure sensor is between
the gas source device and the at least one valve.
7. The system of claim 6, further comprising a second valve and a
second pressure sensor, wherein a second pressure sensor is between
the gas destination device and the second valve.
8. The system of claim 1, wherein upon a decrease in pressure at
the at least one pressure sensor, the controller signals closure of
the at least one valve.
9. The system of claim 1, wherein upon a decrease in pressure at
the at least one pressure sensor or a second pressure sensor, the
controller signals closure of the at least one valve or the
intermediary valve to prevent leakage from the system into an
atmosphere environment.
10. The system of claim 1, further comprising a communication and
switching bus by which the controller commands the at least one
valve to be opened or closed.
11. The system of claim 10, wherein: the at least one valve closes
when not electrically-activated by the controller; and a second
valve closes when not electrically-activated by the controller.
12. The system of claim 11, further comprising an emergency stop
device, wherein: the at least one valve closes when not activated
by electrical power; the second valve closes when not activated by
electrical power; and electrical power is removed from the at least
one valve and second valve when the emergency stop device is
activated.
13. The system of claim 12, wherein upon an increase in pressure of
at least one of the at least one pressure sensor, and a second
pressure sensor, the controller signals closure of the at least one
valve and a second valve to prevent leakage from an atmosphere into
the system.
14. The system of claim 13, wherein upon a decrease in pressure of
at least one of the at least one pressure sensor and the second
pressure sensor, the controller signals closure of the at least one
valve and the second valve to prevent leakage from the system into
an electron microscope.
15. The system of claim 1, wherein the gas destination device
comprises a pump.
Description
FIELD
The invention relates generally to a system and method for safely
controlling the containment of gas within a manifold system and the
delivery of gas to a sample holder for an electron microscope,
e.g., a transmission electron microscope (TEM), a scanning
transmission electron microscopy (STEM) and variations of the
scanning electron microscopes (SEM) that use traditional TEM-type
holders and stages, for imaging and analysis.
BACKGROUND
The options for studying solid and gas interactions in an electron
microscope are limited to a couple of types of systems.
Commercially available environmental scanning/transmission electron
microscope (ESEM/ETEM) technologies create a gaseous environment
close to the object under investigation and enable the atomic scale
study of phenomena occurring during gas-solid interactions. This
gas environment is typically limited to low pressures of less than
15 Torr. Alternatively, for pressures up to 760 Torr or higher,
special gas sample holders, called "environmental sample holders,"
create a sealed gas environment and utilize membranes transparent
to the electron beam to enable the atomic scale study.
The sample holder is a component of an electron microscope
providing the physical support for samples under observation.
Sample holders traditionally used for TEMs and STEMs, as well as
some modern SEMs, consist of a rod that is comprised of three key
regions: the end, the band and the specimen tip. In addition to
supporting the sample, the sample holder provides an interface
between the inside of the instrument (i.e., a vacuum environment)
and the outside world.
To use the sample holder, one or more samples are first placed on a
sample support device. The sample support device is then
mechanically fixed in place at the specimen tip, and the sample
holder is inserted into the electron microscope through a
load-lock. During insertion, the sample holder is pushed into the
electron microscope, assisted by the vacuum within the microscope,
until it stops, which results in the specimen tip of the sample
holder being located in the column of the microscope. At this
point, the barrel of the sample holder bridges the space between
the inside of the microscope and the outside of the load lock, and
the end of the sample holder is outside the microscope. To maintain
an ultra-high vacuum environment inside the electron microscope,
flexible o-rings are typically found along the barrel of the sample
holder, and these o-rings seal against the microscope when the
sample holder is inserted. The exact shape and size of the sample
holder varies with the type and manufacturer of the electron
microscope, but each holder contains the three aforementioned key
regions.
The sample holder can also be used to provide stimulus to the
sample, and this stimulus can include temperature (e.g., heating or
cooling), electricity (e.g., applying a voltage or current),
mechanical (e.g., applying stress or strain), gas or liquid (e.g.,
containing a sample in a specific gaseous or liquid environment),
or several at once. For example, a gas delivery system can be used
to move gas to a sample during imaging. This equipment is outside
of the microscope, and various connectors are used to bring this
stimulus to the sample holder, down the length of the holder, and
to the samples. For example, microfluidic tubing can be used to
supply gas from a gas delivery system to the sample.
One configuration is an environmental cell wherein two
semiconductor devices comprising thin windows are used, and samples
are sandwiched between the two semiconductor devices, and the
environment in proximity of the sample, including an electrical
field and a gas or liquid flow, can be precisely controlled. The
present applicant previously described novel apparatuses and
methods to contact and align devices used to form liquid or gas
cells in International Patent Application No. PCT/US2011/46282
filed on Aug. 2, 2011 entitled "ELECTRON MICROSCOPE SAMPLE HOLDER
FOR FORMING A GAS OR LIQUID CELL WITH TWO SEMICONDUCTOR DEVICES,"
which is hereby incorporated herein by reference in its
entirety.
Disadvantageously, to date, environmental sample holders have had
only limited availability, in part because these holders have
lacked a gas delivery system with the necessary safety
controls.
Environmental sample holders typically require the user to flow a
gas or gases of interest into and out of the holder. The electron
microscope requires a high vacuum to function, and therefore a leak
from the gas sample holder into the microscope would be
problematic. For example, the leak would contaminate components
inside the microscope. A worse case event would be irreparable
damage to the FEG (Field Emission Gun). Therefore, it is important
to have a system that can detect and/or prevent and/or stop gas
leaks inside the electron microscope that could cause damage.
Furthermore, the gas being delivered to the holder could be harmful
if exposed to the environment outside of the microscope. For
example, a toxic gas leaked into the environment could harm a
person or a volatile gas could result in a fire or explosion.
Therefore, it is important to have a system that can detect and/or
prevent and/or stop gas that could be dangerous (toxic or volatile)
from entering the human environment.
Additionally, combining two or more dissimilar gases together may
not be safe as it could result in a reaction and/or a harmful
mixture. A system that can prevent mixing of gases from occurring,
until desired, will make a gas delivery system inherently
safer.
Accordingly, a gas delivery system that can detect and react safely
to leaks and other gas safety issues is needed and is described
herein.
SUMMARY
The invention relates generally to a system and method for safely
controlling the containment of gas within a manifold system and the
delivery of gas to a sample holder for an electron microscope for
imaging and analysis.
In one aspect, a gas delivery system is described, said system
comprising an environmental electron microscope sample holder with
at least one inlet port and at least one outlet port wherein the at
least one inlet port is communicatively connected to a tank T1 and
the at least one outlet port is communicatively connected to a tank
T2 such that at least one gas can travel from tank T1 through the
sample holder to tank T2, said gas delivery system further
comprising at least one pressure sensor and at least one valve,
wherein the at least one pressure sensor is monitored using
controls software with logic that is programmed to identify a leak
in the system and the controls software will signal the closure of
the at least one valve if a leak is detected.
In another aspect, a gas delivery system is described, said system
comprising an environmental electron microscope sample holder with
at least one inlet port and at least one outlet port wherein the at
least one inlet port is communicatively connected to a tank T1 and
the at least one outlet port is communicatively connected to a tank
T2 such that at least one gas can travel from tank T1 through the
sample holder to tank T2, said gas delivery system further
comprising at least one pressure sensor and at least one valve,
wherein the at least one pressure sensor is monitored using
controls software with logic that is programmed to identify a leak
in the system and the controls software will signal the closure of
the at least one valve if a leak is detected, further comprising at
least one set of components communicatively connected and selected
from the group consisting of
(a) a pressure sensor S1 and a valve V1 between tank T1 and the at
least one inlet port, optionally wherein the pressure sensor S1 is
attached to the tank T1;
(b) pressure sensor S2 and a valve V2 between tank T2 and the at
least one outlet port, optionally wherein the pressure sensor S2 is
attached to the tank T2;
(c) a pressure sensor SH for sensing the pressure within the sample
holder and a valve VH between valve V1 and the at least one inlet
port;
(d) a mechanical vacuum pump with a valve VP positioned between the
mechanical vacuum pump and the rest of the system; and
(e) any combination of (a)-(e).
In yet another aspect, a gas delivery system is described, said
system comprising an environmental electron microscope sample
holder with at least one inlet port and at least one outlet port
wherein the at least one inlet port is communicatively connected to
a tank T1 and the at least one outlet port is communicatively
connected to a tank T2 such that at least one gas can travel from
tank T1 through the sample holder to tank T2, said gas delivery
system further comprising at least one pressure sensor and at least
one valve, wherein the at least one pressure sensor is monitored
using controls software with logic that is programmed to identify a
leak in the system and the controls software will signal the
closure of the at least one valve if a leak is detected, further
comprising at least one set of components communicatively connected
and selected from the group consisting of
(a) a pressure sensor S1 and a valve V1 between tank T1 and the at
least one inlet port, optionally wherein the pressure sensor S1 is
attached to the tank T1;
(b) a pressure sensor S2 and a valve V2 between tank T2 and the at
least one outlet port, optionally wherein the pressure sensor S2 is
attached to the tank T2;
(c) a pressure sensor SH for sensing the pressure within the sample
holder and a valve VH between valve V1 and the at least one inlet
port;
(d) a mechanical vacuum pump with a valve VP positioned between the
mechanical vacuum pump and the rest of the system; and
(e) tank T3 which is communicatively connected to the tubing
connecting valve V1 and valve VH, such that tank T3 can be in fluid
communication with tank T1 and gas can travel between tank T3 and
tank T1, and wherein a valve V3 is positioned between tank T3 and
the tubing connecting valve V1 and valve VH.
In still another aspect, a method of purging a gas delivery system
of an environmental electron microscope holder is described, said
method comprising opening valves V1, V2, VH and VP of a system, and
evacuating gas from the system to a pressure P1, as detected by
pressure sensors S1 and/or S2, wherein the system comprises an
environmental electron microscope sample holder with at least one
inlet port and at least one outlet port wherein the at least one
inlet port is communicatively connected to a tank T1 and the at
least one outlet port is communicatively connected to a tank T2
such that at least one gas can travel from tank T1 through the
sample holder to tank T2, said gas delivery system further
comprising at least one pressure sensor and at least one valve,
wherein the at least one pressure sensor is monitored using
controls software with logic that is programmed to identify a leak
in the system and the controls software will signal the closure of
the at least one valve if a leak is detected, further comprising at
least one set of components communicatively connected and selected
from the group consisting of
(a) a pressure sensor S1 and a valve V1 between tank T1 and the at
least one inlet port, optionally wherein the pressure sensor S1 is
attached to the tank T1;
(b) a pressure sensor S2 and a valve V2 between tank T2 and the at
least one outlet port, optionally wherein the pressure sensor S2 is
attached to the tank T2;
(c) a pressure sensor SH for sensing the pressure within the sample
holder and a valve VH between valve V1 and the at least one inlet
port;
(d) a mechanical vacuum pump with a valve VP positioned between the
mechanical vacuum pump and the rest of the system.
Another aspect relates to a method of filling a tank T1 of a gas
delivery system of an environmental electron microscope holder with
an experiment gas, said method comprising closing valves V2, VH and
VP of a system; opening valves V1 and V3 and allowing gas to flow
from tank T3 to tank T1 until a pressure P1 is achieved as
determined by pressure sensor S1, wherein the system comprises an
environmental electron microscope sample holder with at least one
inlet port and at least one outlet port wherein the at least one
inlet port is communicatively connected to a tank T1 and the at
least one outlet port is communicatively connected to a tank T2
such that at least one gas can travel from tank T1 through the
sample holder to tank T2, said gas delivery system further
comprising at least one pressure sensor and at least one valve,
wherein the at least one pressure sensor is monitored using
controls software with logic that is programmed to identify a leak
in the system and the controls software will signal the closure of
the at least one valve if a leak is detected, further comprising at
least one set of components communicatively connected and selected
from the group consisting of
(a) a pressure sensor S1 and a valve V1 between tank T1 and the at
least one inlet port, optionally wherein the pressure sensor S1 is
attached to the tank T1;
(b) a pressure sensor S2 and a valve V2 between tank T2 and the at
least one outlet port, optionally wherein the pressure sensor S2 is
attached to the tank T2;
(c) a pressure sensor SH for sensing the pressure within the sample
holder and a valve VH between valve V1 and the at least one inlet
port;
(d) a mechanical vacuum pump with a valve VP positioned between the
mechanical vacuum pump and the rest of the system.
Yet another aspect relates to a method of flowing gas through an
environmental electron microscope sample holder, said method
comprising opening valves V1, VH and V2 of a system and permitting
the gas to flow from tank Ti through the sample holder to tank T2,
wherein the system comprises an environmental electron microscope
sample holder with at least one inlet port and at least one outlet
port wherein the at least one inlet port is communicatively
connected to a tank T1 and the at least one outlet port is
communicatively connected to a tank T2 such that at least one gas
can travel from tank T1 through the sample holder to tank T2, said
gas delivery system further comprising at least one pressure sensor
and at least one valve, wherein the at least one pressure sensor is
monitored using controls software with logic that is programmed to
identify a leak in the system and the controls software will signal
the closure of the at least one valve if a leak is detected,
further comprising at least one set of components communicatively
connected and selected from the group consisting of
(a) a pressure sensor S1 and a valve V1 between tank T1 and the at
least one inlet port, optionally wherein the pressure sensor S1 is
attached to the tank T1;
(b) a pressure sensor S2 and a valve V2 between tank T2 and the at
least one outlet port, optionally wherein the pressure sensor S2 is
attached to the tank T2;
(c) a pressure sensor SH for sensing the pressure within the sample
holder and a valve VH between valve V1 and the at least one inlet
port;
(d) a mechanical vacuum pump with a valve VP positioned between the
mechanical vacuum pump and the rest of the system.
Still another aspect relates to a method of preventing gas leakage
into an electron microscope from an environmental electron
microscope sample holder, wherein pressure electron microscope
(p.sub.EM)<pressure of tank T1 (p.sub.T1)<atmospheric
pressure (p.sub.atm), said method comprising monitoring pressure
sensors S1, S2 and SH of a system, wherein a decrease in pressure
at at least one of pressure sensors S1, S2 and SH indicates a leak
into the electron microscope, and closing any open valves, wherein
the system comprises an environmental electron microscope sample
holder with at least one inlet port and at least one outlet port
wherein the at least one inlet port is communicatively connected to
a tank T1 and the at least one outlet port is communicatively
connected to a tank T2 such that at least one gas can travel from
tank T1 through the sample holder to tank T2, said gas delivery
system further comprising at least one pressure sensor and at least
one valve, wherein the at least one pressure sensor is monitored
using controls software with logic that is programmed to identify a
leak in the system and the controls software will signal the
closure of the at least one valve if a leak is detected, further
comprising at least one set of components communicatively connected
and selected from the group consisting of
(a) a pressure sensor S1 and a valve V1 between tank T1 and the at
least one inlet port, optionally wherein the pressure sensor S1 is
attached to the tank T1;
(b) a pressure sensor S2 and a valve V2 between tank T2 and the at
least one outlet port, optionally wherein the pressure sensor S2 is
attached to the tank T2;
(c) a pressure sensor SH for sensing the pressure within the sample
holder and a valve VH between valve V1 and the at least one inlet
port;
(d) a mechanical vacuum pump with a valve VP positioned between the
mechanical vacuum pump and the rest of the system.
In another aspect, a method of preventing gas leakage into an
environment outside of a gas delivery system of an environmental
electron microscope sample holder is described, wherein pressure
electron microscope (p.sub.EM)<pressure of tank T1
(p.sub.T1)>atmospheric pressure (p.sub.atm), said method
comprising monitoring pressure sensors S1, S2 and SH of a system,
wherein a decrease in pressure of at least one of pressure sensors
S1, S2 and SH indicates a leak into the environment, and closing
any open valves, wherein the system comprises an environmental
electron microscope sample holder with at least one inlet port and
at least one outlet port wherein the at least one inlet port is
communicatively connected to a tank T1 and the at least one outlet
port is communicatively connected to a tank T2 such that at least
one gas can travel from tank T1 through the sample holder to tank
T2, said gas delivery system further comprising at least one
pressure sensor and at least one valve, wherein the at least one
pressure sensor is monitored using controls software with logic
that is programmed to identify a leak in the system and the
controls software will signal the closure of the at least one valve
if a leak is detected, further comprising at least one set of
components communicatively connected and selected from the group
consisting of
(a) a pressure sensor S1 and a valve V1 between tank T1 and the at
least one inlet port, optionally wherein the pressure sensor S1 is
attached to the tank T1;
(b) a pressure sensor S2 and a valve V2 between tank T2 and the at
least one outlet port, optionally wherein the pressure sensor S2 is
attached to the tank T2;
(c) a pressure sensor SH for sensing the pressure within the sample
holder and a valve VH between valve V1 and the at least one inlet
port;
(d) a mechanical vacuum pump with a valve VP positioned between the
mechanical vacuum pump and the rest of the system.
Other aspects, features and embodiments of the invention will be
more fully apparent from the ensuing disclosure and appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a typical electron microscope sample holder
having two ports for gas or liquid to flow into and out of a cavity
at the tip of the holder.
FIG. 2a is a plan view of an embodiment of the closed sample holder
cell with the sample holder cover on. FIG. 2b is a plan view of the
sample holder cell of FIG. 2a with the sample holder cover off.
FIG. 2c is a plan view of the sample holder cell of FIG. 2b with
the large MEMS chip removed. FIG. 2d is a plan view of the sample
holder cell of FIG. 2c with the small MEMS chip removed.
FIG. 3a depicts the components for an embodiment of the system that
can deliver gas to an environmental cell sample holder, wherein
said system includes two tanks.
FIG. 3b depicts a system of FIG. 3a including two valves (V1, V2)
and two pressure sensors (S1, S2).
FIG. 3c depicts a system of FIG. 3b including a mechanical vacuum
pump and valve VP.
FIG. 3d depicts a system of FIG. 3c including Tank 3, pressure
sensor S3 and Valve V3, and Valve VH upstream from the holder.
FIG. 3e depicts a system of FIG. 3d including external Tank 4 and
Tank 5, valves V4, V5 and pressure sensors S4.
FIG. 3f depicts a system of FIG. 3e including a pressure sensor SH
inside the TEM holder.
FIG. 3g depicts a system of FIG. 3f including an interface
controller with software as well as a communication and switching
bus.
FIG. 4a is a block diagram of the system of FIGS. 3a-3g.
FIG. 4b is a block diagram of an advanced system.
FIG. 5a illustrates an example of the purge of the system of FIG.
3g.
FIG. 5b illustrates an example of the filling, or backfill, of Tank
1 of FIG. 5a with the experiment gas.
FIG. 5c illustrates an example of a gas flow experiment using the
system of FIG. 5b.
FIG. 5d illustrates the end use of the system of FIG. 5c.
FIG. 5e illustrates the purge of the system of FIG. 5d.
FIG. 5f illustrates the return of the system of FIG. 5e to its
initial stage by backfilling with nitrogen.
DETAILED DESCRIPTION
The sample holder of the present disclosure is broadly illustrated
in FIG. 1, wherein the sample holder includes tubing inside the
electron microscope (EM) holder that travels to and from the closed
cell at the specimen tip. The placement of the tubing is just for
general illustration and is not intended to limit the holder in any
way. The tubing permits fluids, e.g., gases or liquids, to travel
to and from the closed cell, for in situ analysis of the sample
positioned in the closed cell. The general area of "in situ"
electron microscopy involves applying stimulus to a sample during
imaging. The stimulus could be thermal (heating or cooling),
electrical (applying a voltage or current), mechanical (applying
stress or strain), chemical (containing a sample in a specific
chemical environment), or several of these at once.
FIGS. 2a-2d illustrate an example of the closed cell that is
positioned at the specimen tip of FIG. 1. The closed cell in FIGS.
2a-2d is just for general illustration and is not intended to limit
the closed cell in any way. FIG. 2a is a plan view of the closed
cell, wherein a cover of the closed cell is shown positioned and
affixed, e.g., with screws, to the cell. FIG. 2b is a plan view of
the closed cell with the cover off, revealing the first of two MEMS
chips (i.e., a sample support device) positioned in the cell. FIG.
2c is a plan view of the closed cell showing the second of two MEMS
chips after the first MEMS chip is removed. The large and small
MEMS chips are stacked on top of one another and the sample can be
"sandwiched" between the two chips (not shown). FIG. 2c also
reveals the first of two O-rings, which is positioned below the
large MEMS chip to seal the cell so liquid or gas can be introduced
into the cell. FIG. 2d is a plan view of the closed cell showing
the bottom of the cell after the second MEMS chip is removed. FIG.
2d also reveals the second of two O-rings, which is positioned
below the small MEMS chip to form the second seal so liquid or gas
can be introduced into the cell. The fluidic reservoir in FIG. 2d
corresponds to the area between the two O-rings when the MEMS chips
are in place. Although not illustrated in FIGS. 2a-2d per se, the
fluidic reservoir indicated in FIG. 2d has depth to accommodate the
MEMS chips. It should be appreciated that the "closed cell" remains
in fluid communication with fluidic inlets and hence the closed
cell receives gasses from an external source and gasses are
returned from the closed cell to an external source. It is to be
understood that the closed cell described herein is compatible with
and may be interfaced with the sample support devices, e.g.,
semiconductor sample support devices, disclosed in International
Patent Application Nos. PCT/US08/63200 filed on May 9, 2008,
PCT/US11/46282 filed on Aug. 2, 2011, and PCT/US08/88052 filed on
Dec. 22, 2008, which are all incorporated herein by reference in
their entireties. It should also be appreciated by one skilled in
the art that alternative sample support devices may be interfaced
with the closed cell described herein. The closed cell provides
mechanical support for one or more samples or sample support
devices and also provides other stimuli (e.g., temperature,
electricity, mechanical, chemical, gas or liquid, or any
combination thereof) to the samples or sample support devices. The
closed cell can be manufactured with tips, barrels and ends of
various shapes and sizes such that the sample holder fits any
manufacturer's electron microscope.
As used herein, a "sample support device" corresponds to a
structure that holds a sample for microscopic imaging. A sample
support device can provide an experimental region. Devices may
include one, more than one or even an array of experimental regions
and may include integrated features such as electrodes,
thermocouples, and/or calibration sites, as readily determined by
one skilled in the art. One preferred embodiment includes sample
support devices made with MEMS technology and with thin membranes
(continuous or perforated) for supporting a sample in the
experimental region. Sample support devices include, but are not
limited to, a window device, an electrical device and a heating
device.
As defined herein, the term "tank" is intended to mean a source of
gas at a pressure. Typically a tank would be a hermetic enclosure.
Alternatively, in some cases, it could be atmospheric air or a mass
flow controller.
FIG. 3a depicts an embodiment of a system that can deliver gas to
an environmental cell sample holder. The TEM holder is connected to
a tank T1 with gas at pressure P1 and a tank T2 initially without
gas at pressure P2, where both tanks are connected with tubing to
an inlet and an outlet of the holder, respectively. Pressure P1 is
at a higher pressure than P2 and therefore the gas will flow from
tank T1 through the holder and into tank T2. Without further
components, the pressure(s) in the system cannot be monitored and
the gas flow cannot be quickly and easily stopped.
FIG. 3b depicts a system that adds two valves (V1, V2) and two
pressure sensors (S1, S2) to the system of FIG. 3a. The valves
would allow the gas stream to be open or closed. Depending on the
type of valve, the valve could be opened mechanically (i.e., by
hand) or electronically by a controller. Some types of valves, like
a needle valve, can add a variable restriction to regulate the rate
of gas flow. A type of valve preferred in this system is a normally
closed electrically-activated solenoid valve, such as p/n
6LVV-DPFR4-P1-CM offered by Swagelok. Because they can be used in
controls automation, electronic pressure sensors are the preferred
type of pressure sensor for this system. Pressure sensors such as
the "Baritron" brand offered by MKS Instruments are able to provide
real time pressure values. These values are used to establish the
desired state of gas and pressure within a region of the system.
These components in FIG. 3b enable the pressure in the tanks to be
monitored and also allow for the closure of the gas line between
the tanks and the holder. Because the preferred pressure sensors
and valves in this embodiment are intended for use with controls
automation, additional equipment including a controller and
software may be necessary, as described later. Although FIG. 3b
displays sensors S1 and S2 between the tanks and the valve, the
sensors could be attached to the tank itself with equal results,
which is true for all display sensors described in the present
disclosure.
FIG. 3c adds a mechanical vacuum pump and valve VP to the system.
The primary purpose of the pump is to remove gas from the system or
parts of the system. For example, Tank 2 will eventually fill with
the gas being delivered from Tank 1 and a vacuum pump is an easy
way to remove these gases. Typical use cases including the use of
the pump and valve VP will be described in more detail later.
Depending on the toxicity or volatility of the gases being used,
the mechanical vacuum pump will send the exhausted gas to a safe
location away from harm, such as into a fume hood or directly
outside the building.
FIG. 3d adds Tank 3, pressure sensor S3 and Valve V3, and Valve VH
to the system of FIG. 3c, upstream from the holder. Tank 3 is
intended to be external to the rest of the manifold for the purpose
of being disconnected so that it can be refilled or replaced when
empty, or replaced with a tank containing a different gas. Tank 3
will be at a pressure greater than Tank 1, such that gas from Tank
3 can be flowed into Tank 1 until the desired pressure P1 is
achieved. P1 is dependent on what pressure the user wants to
achieve in the TEM holder. By having tank 3 at a higher pressure
(i.e., more gas), tank 1 can be replenished whenever needed until
the gas in tank 3 is exhausted. This can be done by opening the
valves V1, V3 between tank 1 and tank 3, closing valves V2, VP, and
VH, and when the pressure sensor S1 read the desired pressure for
Tank 1, the valves are closed.
FIG. 3e adds external Tank 4 and Tank 5, valves V4, V5 and pressure
sensors S4 and S5 to the system of FIG. 3d. The addition of Tank 4
and 5 and their associated valves V4, V5 and sensors S4 and S5 is
to allow at least 3 different gases to be connected to the manifold
at one time. This makes the system much easier to use because the
user will not need to physically replace Tank 3 if a different gas
is desired to be used in the system. It is also highly desired that
one of the three external tanks 3, 4, or 5 contains what is
referred to as a purge gas. A purge gas is a gas used to displace
unwanted gas from the system, typically done before and/or after an
experiment has been completed.
FIG. 3f adds a pressure sensor SH inside the TEM holder of the
system of FIG. 3e. The present applicant previously described novel
apparatuses and methods to sense pressure and other states inside
liquid or gas cells in US Provisional Patent Application No.
61/941,743 filed on Feb. 19, 2014, and International Patent
Application No. PCT/US2015/016562 filed on Feb. 19, 2015, both
entitled "METHOD FOR MONITORING ENVIRONMENTAL STATES OF A
MICROSCOPE SAMPLE WITH AN ELECTRON MICROSCOPE SAMPLE HOLDER," which
are hereby incorporated herein by reference in their entirety.
Measuring the pressure in the region of the sample provides the
user more accurate information about the gas environment of the
sample. By monitoring the pressure at the region of the sample
which is at the membranes of the TEM holder, the system should more
quickly detect a leak and react accordingly as described later.
FIG. 3g adds an interface controller with software as well as a
communication and switching bus, such as manufactured by WAGO, to
the system of FIG. 3f. The interface controller could be a personal
computer with monitor. The communication and switching bus enables
I/O communication from the pressure sensors, valves, vacuum pump
and the controls software and the ability to change the state of a
device. For example, this allows the software to command the valves
to be opened or closed and monitor the states of all of these
devices in order to make user demanded or programmed decisions.
Although not shown in FIG. 3g, the communication and switching bus
is connected to all of these components (e.g., sensors, valves,
tanks, etc.) with the appropriate manufacturer recommended I/O
cabling. It should be recognized by those skilled in the art that
additional pressure sensors and valves and tanks (not shown) could
provide additional functionality (for example, mixing). Moreover,
other valves and pressure sensors are contemplated for use herein,
as readily determined by the person skilled in the art.
FIG. 4a is a block diagram of the previously described system in
block components 1-6. FIG. 4b is a block diagram of an advanced
system. The advanced system combines additional components 7-10 for
advanced functionality and/or safety. A Mechanical Emergency Stop
device (E-Stop) (7). If the E-Stop is activated, typically by
pressing a red button, the power to the system, or parts of the
system, is removed. E-Stops are commonly available through
industrial supply stores such as Grainger, manufactured by
companies such as Omron. Pressure relief valve(s) (8) are commonly
available through industrial supply stores and will vent gas out of
a system if a pressure reaches a critical level. For example, if a
pressure of 1000 Torr is expected to rupture a membrane in the TEM
holder, a relief valve with a set point of 900 Torr and placed
inline upstream from the TEM holder, preventing the membranes from
reaching 1000 Torr. A mass spectrometer (9) is a piece of
instrumentation used to determine the elemental composition within
a gas. This would be a useful component to use with this system.
Users of this system want to fully understand the reaction of
gasses and solids at the atomic level. This includes determining
what the resultant gas composition is, after a reaction at the
sample area has occurred, if at all. By flowing the gas that exits
the holder into a mass spectrometer, the exact composition of the
resultant gas can be analyzed and information about the gas--solid
reaction can be established. A heater system (10) can be added to
any of the components in the system that encapsulate gas such as
the tanks and tubing. Heating tape and heating wire can be placed
on and/or around these components to raise the temperature of the
surfaces that are in contact with the gas. The purpose of raising
the temperature is to reduce the bond strength of contaminants that
attach to these surfaces during operation. In combination with
cycling a purge gas such as Nitrogen in and then removing the
Nitrogen by driving the pressure to a low level, effective removal
of contaminants can be achieved.
Multiple embodiments are described to show typical use cases on the
system described herein in FIG. 3g, by way of example. i) Use Case
1--Purge System--Before running a gas flow experiment, a typical
use case will be to remove (purge) all of the gas from the system.
To do this, valves V1, V2, VH and VP of the system of FIG. 3g are
opened by the software controls (see, FIG. 5a). The vacuum pump
will remove gas from the tubing and tanks and sample holder to a
base vacuum level P1. For example, P1 could be in a range from
about 0.01 to about 10 milliTorr, preferably about 1 milliTorr.
Once sensors S1 and/or S2 and/or SH reach the P1 pressure, valves
V1, V2, VH and VP will be closed by the software controls. At this
point the system has been purged. ii) Use Case 2--Backfill Tank
1--Next, Tank 1 needs to be filled with the experiment gas. For
example, the user may want to run an experiment with Argon gas at
1500 Torr. Tank 3 contains Argon at a high pressure, e.g., greater
than 1500 Torr. Valves V1 and V3 will open (see, e.g., FIG. 5b)
allowing the gas from Tank 3 to fill Tank 1 until sensor S1
measures a preferred pressure, e.g., about 1500 Torr, at which
point Valves V1 and V3 will close. At this point, tank 1 has been
filled with the experiment gas to the required pressure. iii) Use
Case 3--Gas Flow Experiment--Next valves V1, VH and V2 open (see,
FIG. 5c). Since, by way of example, the pressure in Tank 1 is at
1500 Torr and the pressure in Tank 2 is low, e.g., about 1
milliTorr, Argon gas will flow from Tank 1, through the TEM holder
and into tank 2. When the user wants to stop the experiment, valves
V1, V2 and VH will be closed. iv) User Case 4--Static Gas
Experiment--The end of use Case 3 is effectively a static gas
experiment (see, FIG. 5d). Pressure sensor SH will monitor the
pressure in the sample holder. v) Use Case 5--Purge system. At the
end of the experiment, the next step is to repeat Use Case 1,
removing gases from the system (see, FIG. 5e). vi) User Case
6--Backfill the system with Nitrogen. The system can now be brought
back to its initial state. Tank 5 is filled with Nitrogen at a
pressure at or higher than 760 Torr. By opening valves V1, V2, V5
and VH (see, FIG. 5f), Nitrogen will fill the system until Si
and/or S2 and/or SH measure determine a desired purge pressure has
been achieved. This would typically be atmospheric pressure. The
purpose of using Nitrogen, or some other inert gas, is that it is a
pure safe clean gas, desired when the system is not being used.
The aforementioned use cases are ideal. However, in the event of
leaks or other malfunctioning equipment, automated processes need
to be developed. The following multiple embodiments are associated
with a method of safely controlling the containment of gas within a
manifold system and delivering gas to a sample holder for an
electron microscope. a. Leak detection. Under the conditions of Use
Case 4 above for example, all of the valves in the system are
closed. The controls software (6) is programmed to monitor the
pressure readings from the sensors S 1, S2 and SH, and in the event
of a transient increase in pressure (i.e., a leak into the system)
notify the user of the location and size of the leak. A leak into
the system is highly undesirable as it will allow air to mix with
the experiment gas. b. Leaks into the electron microscope Under the
conditions of Use Case 3 above, when the pressure of the electron
microscope (p.sub.EM) is less than the pressure of tank T1
(p.sub.T1), which is less than atmospheric pressure (p.sub.atm),
pressure sensors S1, S2 and SH are monitoring the pressures in the
system. The software controls (6) are programmed to react in the
event of an electron microscope leak as follows. Electron
microscope columns are maintained at pressures lower than any of
the pressures in the described gas delivery system, with the
possible exception of the pressure in Tank T2. Therefore, an
unexpected decrease in pressure as determined by pressure sensors
S1 and/or S2 and/or SH indicates a leak from the sample holder (1)
into the Electron microscope. The pressure sensors S1 and/or S2
and/or SH will measure this pressure change and the software
controls (6) will close all of the open valves to prevent
additional gas from leaking into the microscope, thus minimizing
damage to the microscope. Additionally, Valve VP may be temporarily
opened to the Mechanical Vacuum Pump forcing the gas in the tubing
to at least partially be evacuated by the Mechanical Vacuum Pump,
further minimizing the amount of gas that is able to escape into
the microscope. This will allow the user to safely shut down the
microscope, remove the sample holder and repair the source of the
leak. Furthermore, if the controls system is connected to the
electron microscope system, it is possible to initiate safety
controls on the microscope as well, such as closing the valve to
the Field Emission Gun. While Use Case 1 was used to explain the
safety controls, it should be appreciated that these controls will
work for all possible use cases where a valve can be closed to
prevent gas from entering the microscope in the event of a leak. c.
Leaks at pressures higher than atmospheric pressure Under the
conditions of Use Case 4 above, when the pressure of the electron
microscope (p.sub.EM) is less than the pressure of tank T1
(p.sub.T1), which is greater than atmospheric pressure (p.sub.atm),
pressure sensors S1, S2 and SH are monitoring the pressures in the
system. The software controls (6) are programmed to react in the
event of an environment leak as follows. In this example, Tank 1
can be at any pressure greater than atmospheric pressure, e.g.,
about 1500 Torr. Therefore, an unexpected decrease in pressure as
determined by pressure sensors S1 and/or S2 and/or SH could
indicate a leak into the environment. The pressure sensors S1
and/or S2 and/or SH will measure this pressure change and the
software controls (6) will open valves V1, VP and VH to allow the
vacuum pump to remove the gas from the system, preventing further
escape into the atmosphere. This will allow the user to safely shut
down the microscope, remove the sample holder and repair the source
of the leak. d. In any of the use cases, the software may lose
partial communication with the system If software is not receiving
the expected communication from the system, it will send a command
to remove power from the valves. Since all of the valves in the
system are normally closed, removing power will close any open
valves. This could occur in the event of a software defect,
operating system defect, computer malfunction or a cable break. All
valves will remain closed until the software controls are
functioning. If software is not working properly or at all, for
example it has crashed or is frozen up, it may not be possible for
the user to determine if there is a leak in the system. In this
event the user can activate the mechanical emergency stop device
(E-Stop), as described above. Since all of the valves in the system
are normally closed, the E-stop will stop power to these valves.
All valves will remain closed until the software controls are
functioning. e. Mixing gases When mixing gases in the system is
prohibited, safety controls to prevent mixing gases is important.
In many cases, mixing dissimilar gases could be unsafe. For
example, the resultant mixture could be toxic or volatile. To
prevent this, if a valve is commanded to open by the user, and it
is between two areas of the system with dissimilar gases, the
system will not open the valve. The need for this control could
arise in the event of an operator error or a software defect. For
example, the software may be written in a way to allow the user to
freely control a valve to open or close. However, the software will
recognize if the valve being opened will cause a safety issue and
prevent it from occurring. In a similar scenario, if a valve opens
between two containers with dissimilar gases, then the system will
automatically shut the valve. The need for this control could
arise, for example, in a failure of one or more electro-mechanical
components.
While the invention has been described herein in reference to
specific aspects, features and illustrative embodiments of the
invention, it will be appreciated that the utility of the invention
is not thus limited, but rather extends to and encompasses numerous
other variations, modifications and alternative embodiments, as
will suggest themselves to those of ordinary skill in the field of
the present invention, based on the disclosure herein.
Correspondingly, the invention as hereinafter claimed is intended
to be broadly construed and interpreted, as including all such
variations, modifications and alternative embodiments, within its
spirit and scope.
* * * * *